The Cromer crab sandwich is a sandwich whose identity is a stretch of the Norfolk coast. The crab landed at Cromer is a small one, worked over chalk reef in cold water, and it is prized for a sweet, dense meat in a higher proportion than larger crabs give up. That is the entire premise: not crab in general but this particular small, sweet, local crab, picked fresh and put on bread with as little done to it as the kitchen can manage. The locality is not a label on a generic crab sandwich. It is the reason the sandwich is named at all, and the reason a heavy hand with the dressing is treated as a fault rather than a flavour.
The craft is restraint and freshness. The picked meat is bound only just enough to hold, often with no more than a light bind and a squeeze of lemon, because the point is to taste the crab and a thick sauce simply masks the sweetness the Cromer catch is famous for. The white and brown meat are usually kept distinct or layered rather than blended into a single paste, so a bite carries both the clean sweetness of the white and the richer, deeper note of the brown. The bread is plain and soft, white or lightly brown, buttered thin to bridge the crumb and the meat without adding a flavour of its own, and the crab is piled rather than spread so it reads as a portion of shellfish, not a smear. It is a sandwich made the day the crab is picked, because the meat is delicate and short-lived and a tired crab undoes the whole reason for choosing this one.
The variations stay deliberately small, since the brief is to get out of the crab's way. A little cucumber adds a cool, watery snap; a dressed version layers picked white over the seasoned brown; samphire from the same coast brings a saline, crisp counter. Each is a distinct coastal pairing and deserves its own article rather than being crowded in here.